Visual Discrimination in the Cat: IV. The Visual Acuity of the Cat in Relation to Stimulus Distance

1936 ◽  
Vol 49 (2) ◽  
pp. 297-313
Author(s):  
Karl U. Smith
Keyword(s):  
Visual Acuity ◽  
Visual Discrimination ◽  
Stimulus Distance

scholarly journals A horse's eye view: size and shape discrimination compared with other mammals

2015 ◽  
Vol 11 (11) ◽  
pp. 20150701 ◽  
Author(s):  
Masaki Tomonaga ◽  
Kiyonori Kumazaki ◽  
Florine Camus ◽  
Sophie Nicod ◽  
Carlos Pereira ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Cognitive Abilities ◽  
Visual Discrimination ◽  
Natural Environments ◽  
Perceptual Similarity ◽  
Shape Discrimination ◽  
Size And Shape ◽  
Circle Size ◽  
Computer Controlled

Mammals have adapted to a variety of natural environments from underwater to aerial and these different adaptations have affected their specific perceptive and cognitive abilities. This study used a computer-controlled touchscreen system to examine the visual discrimination abilities of horses, particularly regarding size and shape, and compared the results with those from chimpanzee, human and dolphin studies. Horses were able to discriminate a difference of 14% in circle size but showed worse discrimination thresholds than chimpanzees and humans; these differences cannot be explained by visual acuity. Furthermore, the present findings indicate that all species use length cues rather than area cues to discriminate size. In terms of shape discrimination, horses exhibited perceptual similarities among shapes with curvatures, vertical/horizontal lines and diagonal lines, and the relative contributions of each feature to perceptual similarity in horses differed from those for chimpanzees, humans and dolphins. Horses pay more attention to local components than to global shapes.

scholarly journals ON THE VARIABILITY OF CRITICAL ILLUMINATION FOR FLICKER FUSION AND INTENSITY DISCRIMINATION

1936 ◽  
Vol 19 (3) ◽  
pp. 503-522 ◽  
Author(s):  
W. J. Crozier
Keyword(s):  
Visual Acuity ◽  
General Problem ◽  
Visual Function ◽  
Visual Discrimination ◽  
Dark Adaptation ◽  
Intensity Discrimination ◽  
The Sun ◽  
Threshold Response ◽  
Independent Variable ◽  
Flicker Fusion

From the data of experiments with bees in which threshold response is employed as a means of recognizing visual discrimination between stripes of equal width alternately illuminated by intensities I1 and I2, it is shown that the detectable increment of intensity ΔI, where ΔI = I2 - I1, is directly proportional to σI2 (I1 being fixed). From tests of visual acuity, where I1 = 0 and the width of the stripes is varied, σI2 = kI2 + const.; here I2 = ΔI, and ΔI/I2 = 1. When the visual excitability of the bee is changed by dark adaptation, λI ≡ kΔI (= k' σΔI) = k'' I + const. For the measurements of critical illumination at threshold response to flicker, σI2 (= σΔI) = k I2 = k' ΔI + const. The data for critical illumination producing threshold response to flicker in the sun-fish Lepomis show for the rods σI2 = K I2 for the cones σI2 = K'(I2 + const.). The data thus indicate that in all these experiments essentially the same visual function is being examined, and that the recognition of the production of a difference in effect by alternately illuminated stripes takes place in such a way that d (ΔI)/d (σI2) = const., and that ΔI is directly proportional to I (or "I2," depending on the nature of the experiment). It is pointed out that the curve for each of the cases considered can be gotten equally well if mean I or σI is plotted as a function of the independent variable involved in the experiment. Certain consequences of these and related facts are important for the treatment of the general problem of intensity discrimination.

Are Rats Short-Sighted? Effects of Stimulus Distance and Size on Visual Detection

1981 ◽  
Vol 33 (2b) ◽  
pp. 69-76 ◽  
Author(s):  
Paul Dean
Keyword(s):  
Visual Acuity ◽  
Present Experiment ◽  
Visual Angle ◽  
Visual Detection ◽  
Visual Stimuli ◽  
Good Evidence ◽  
Physical Size ◽  
Stimulus Distance ◽  
Behavioural Evidence

Behavioural evidence concerning short-sightedness in rats is apparently conflicting: in some experiments rats have performed poorly with visual stimuli further than about 60 cm distant, while in others they have made efficient use of more distant cues, for example to find their way through mazes. However, in the experiments suggesting short-sightedness, the physical size of the stimuli was not varied, so that stimulus distance and visual angle were confounded. In the present experiment, therefore, the size and distance of the stimuli to be detected were varied independently. Over the range tested (30–160 cm), distance was found to produce relatively slight effects on the smallest detectable visual angle, and these tended to diminish with practice. Thus, no good evidence was found for short-sightedness in rats up to 160 cm, a finding consistent with current views of the structure and image-forming capacities of the rat's eye. The smallest detectable targets were, however, surprisingly large in view of the rat's visual acuity (which is about 1c/deg): at the distances tested, animals required considerable training to run reliably to targets subtending less than 5–10° of visual angle. Difficulties in responding to stationary stimuli of this size are likely to restrict severely the use that rats make of vision both in the laboratory and in their natural surroundings.

Visual-discrimination deficits after lesions of the centrifugal visual system in pigeons (Columba livia)

1992 ◽  
Vol 9 (3-4) ◽  
pp. 225-233 ◽  
Author(s):  
Uwe Hahmann ◽  
Onur Güntürkün
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Early Detection ◽  
Visual System ◽  
Visual Discrimination ◽  
Visual Analysis ◽  
Linear Regression Analysis ◽  
Columba Livia ◽  
Viewing Distance ◽  
Bilateral Lesions

AbstractThe effects of bilateral lesions of the centrifugal visual system (CVS) on the visual-discrimination capacity were studied in pigeons. Three different behavioral experiments, each testing different aspects of visual analysis, were performed. In the first two experiments, a grain-grit discrimination task and a visual-acuity determination, stimuli were presented in the frontal binocular visual field. A third experiment investigated the early detection of slow moving objects, introduced into the monocular lateral visual field. After bilateral lesions in the nucleus isthmo-opticus (ION) and in the ectopic nucleus isthmo-opticus (EION), a multiple linear regression analysis was employed to correlate the postoperative performance in all three tasks with the amount of structure loss within ION and EION. Deficits in the grain-grit discrimination procedure were a function of the ION lesion extent and did not depend on EION damage. Thus, these two structures could be functionally differentiated for the first time. Neither the ION nor the EION seems to be involved in visual- acuity performance or the early detection of large shadows moving forward through the visual field. Our data support the hypothesis that the CVS is involved in pecking and food selection among static stimuli at a short viewing distance in ground-feeding birds such as pigeons and chickens.

X-Ray Microanalysis of Nickel and Cobalt Intensified Peroxidase- Antiperoxidase For Verification of Reaction Sites

1985 ◽  
Vol 43 ◽  
pp. 468-469
Author(s):  
A. Angel ◽  
K. Miller ◽  
V. Seybold ◽  
R. Kriebel
Keyword(s):  
Reaction Mechanisms ◽  
Visual Discrimination ◽  
Osmium Tetroxide ◽  
Ultrastructural Level ◽  
Microscopic Level ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
X Ray ◽  
Insoluble Polymer ◽  
Cytochemical Reaction

Localization of specific substances at the ultrastructural level is dependent on the introduction of chemicals which will complex and impart an electron density at specific reaction sites. Peroxidase-antiperoxidase(PAP) methods have been successfully applied at the electron microscopic level. The PAP complex is localized by addition of its substrate, hydrogen peroxide and an electron donor, usually diaminobenzidine(DAB). On oxidation, DAB forms an insoluble polymer which is able to chelate with osmium tetroxide becoming electron dense. Since verification of reactivity is visual, discrimination of reaction product from osmiophillic structures may be difficult. Recently, x-ray microanalysis has been applied to examine cytochemical reaction precipitates, their distribution in tissues, and to study cytochemical reaction mechanisms. For example, immunoreactive sites labelled with gold have been ascertained by means of x-ray microanalysis.

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